In the fabrication of microelectronic components, a number of the steps involved, for instance, in preparing integrated circuit chips and the packaging for the chips (articles to which the chips are attached and protected), are etching processes. Accordingly, over the years, a number of vastly different types of etching processes to remove material, sometimes in selective areas, have been developed and are utilized to varying degrees. Moreover, the steps of etching different layers which constitute, for instance, the finished integrated circuit chip are among the most critical and crucial steps.
One method widely employed for etching is to overlay the surface to be etched with a suitable mask and then immerse the surface and mask in a chemical solution which attacks the surface to be etched, while leaving the mask intact and while only etching other materials of the article to at most, a minimum extent. These techniques are commonly referred to as wet etching.
Increasingly, reactive ion etching (RIE), plasma etching and ion milling are being used to define the pattern in a substrate and to form trenches which expose the semiconductor substrate such as silicon. The RIE process leaves residues on the semiconductor in the trenches of a complex mixture that may include re-sputtered oxide material and possibly small amounts of organic material from the resists used to delineate the trenches, including deep trenches.
Accordingly, these residues must be removed without adversely affecting those materials which are to remain as part of the article.
Furthermore, etching processes such as reactive ion etching (RIE), plasma etching and ion milling are typically carried out employing as mask materials a silicate glass, silicate esters such as tetraethylorthosilicide and silicon oxynitride. After the etching procedure, the remaining mask materials are also removed and must be done without adversely affecting those materials which are to remain as part of the article.
Furthermore, in many devices it is desirable to remove selected portions of silicon nitride layers and/or silicon dioxide layers such as in forming recesses again without adversely affecting those materials which are to remain as part of the article. In many such structures, a silicon nitride layer exists on top or beneath a silicon dioxide layer and it becomes necessary to etch the silicon nitride without over-etching the silicon dioxide. The ability to use an aqueous fluoride solution such as aqueous hydrogen fluoride in such situation presents a problem since aqueous hydrogen fluoride etches silicon dioxide at a much faster rate than it does silicon nitride.
In order to remove the etching residues, etching mask material and selected portions of silicon nitride and/or silicon dioxide, it has been necessary to use at least three different processing compositions and steps typically employing deionized water rinse and drying steps between each step. For instance, reactive ion etching residues have been removed using BHF; and etching mask using certain HF-sulfuric acid compositions. Etching recesses in silicon nitride/silicon dioxide has been accomplished with certain compositions of HF and glycerol.
It would therefore be desirable to provide an etching procedure that achieves excellent removal of the above materials without adversely affecting those other materials which are to remain as part of the article, at least during subsequent processing, and without the need to employ a plurality of different compositions and processing steps.